﻿// EntityResolver2.java - Extended SAX entity resolver.
// http://www.saxproject.org
// No warranty; no copyright -- use this as you will.
// $Id$
using System;

namespace org.xml.sax.ext
{

    /**
     * Extended interface for mapping external entity references to input
     * sources, or providing a missing external subset.  The
     * {@link XMLReader#setEntityResolver XMLReader.setEntityResolver()} method
     * is used to provide implementations of this interface to parsers.
     * When a parser uses the methods in this interface, the
     * {@link EntityResolver2#resolveEntity EntityResolver2.resolveEntity()}
     * method (in this interface) is used <em>instead of</em> the older (SAX 1.0)
     * {@link EntityResolver#resolveEntity EntityResolver.resolveEntity()} method.
     *
     * <blockquote>
     * <em>This module, both source code and documentation, is in the
     * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
     * </blockquote>
     *
     * <p>If a SAX application requires the customized handling which this
     * interface defines for external entities, it must ensure that it uses
     * an XMLReader with the
     * <em>http://xml.org/sax/features/use-entity-resolver2</em> feature flag
     * set to <em>true</em> (which is its default value when the feature is
     * recognized).  If that flag is unrecognized, or its value is false,
     * or the resolver does not implement this interface, then only the
     * {@link EntityResolver} method will be used.
     * </p>
     *
     * <p>That supports three categories of application that modify entity
     * resolution.  <em>Old Style</em> applications won't know about this interface;
     * they will provide an EntityResolver.
     * <em>Transitional Mode</em> provide an EntityResolver2 and automatically
     * get the benefit of its methods in any systems (parsers or other tools)
     * supporting it, due to polymorphism.
     * Both <em>Old Style</em> and <em>Transitional Mode</em> applications will
     * work with any SAX2 parser.
     * <em>New style</em> applications will fail to run except on SAX2 parsers
     * that support this particular feature.
     * They will insist that feature flag have a value of "true", and the
     * EntityResolver2 implementation they provide  might throw an exception
     * if the original SAX 1.0 style entity resolution method is invoked.
     * </p>
     *
     * @see org.xml.sax.XMLReader#setEntityResolver
     *
     * @since SAX 2.0 (extensions 1.1 alpha)
     * @author David Brownell
     * @version TBD
     */
    public interface EntityResolver2 : EntityResolver
    {
        /**
         * Allows applications to provide an external subset for documents
         * that don't explicitly define one.  Documents with DOCTYPE declarations
         * that omit an external subset can thus augment the declarations
         * available for validation, entity processing, and attribute processing
         * (normalization, defaulting, and reporting types including ID).
         * This augmentation is reported
         * through the {@link LexicalHandler#startDTD startDTD()} method as if
         * the document text had originally included the external subset;
         * this callback is made before any internal subset data or errors
         * are reported.</p>
         *
         * <p>This method can also be used with documents that have no DOCTYPE
         * declaration.  When the root element is encountered,
         * but no DOCTYPE declaration has been seen, this method is
         * invoked.  If it returns a value for the external subset, that root
         * element is declared to be the root element, giving the effect of
         * splicing a DOCTYPE declaration at the end the prolog of a document
         * that could not otherwise be valid.  The sequence of parser callbacks
         * in that case logically resembles this:</p>
         *
         * <pre>
         * ... comments and PIs from the prolog (as usual)
         * startDTD ("rootName", source.getPublicId (), source.getSystemId ());
         * startEntity ("[dtd]");
         * ... declarations, comments, and PIs from the external subset
         * endEntity ("[dtd]");
         * endDTD ();
         * ... then the rest of the document (as usual)
         * startElement (..., "rootName", ...);
         * </pre>
         *
         * <p>Note that the InputSource gets no further resolution.
         * Implementations of this method may wish to invoke
         * {@link #resolveEntity resolveEntity()} to gain benefits such as use
         * of local caches of DTD entities.  Also, this method will never be
         * used by a (non-validating) processor that is not including external
         * parameter entities. </p>
         *
         * <p>Uses for this method include facilitating data validation when
         * interoperating with XML processors that would always require
         * undesirable network accesses for external entities, or which for
         * other reasons adopt a "no DTDs" policy.
         * Non-validation motives include forcing documents to include DTDs so
         * that attributes are handled consistently.
         * For example, an XPath processor needs to know which attibutes have
         * type "ID" before it can process a widely used type of reference.</p>
         * 
         * <p><strong>Warning:</strong> Returning an external subset modifies
         * the input document.  By providing definitions for general entities,
         * it can make a malformed document appear to be well formed.
         * </p>
         *
         * @param name Identifies the document root element.  This name comes
         *	from a DOCTYPE declaration (where available) or from the actual
         *	root element. 
         * @param baseURI The document's base URI, serving as an additional
         *	hint for selecting the external subset.  This is always an absolute
         *	URI, unless it is null because the XMLReader was given an InputSource
         *	without one.
         *
         * @return An InputSource object describing the new external subset
         *	to be used by the parser, or null to indicate that no external
         *	subset is provided.
         *
         * @exception SAXException Any SAX exception, possibly wrapping
         *	another exception.
         * @exception IOException Probably indicating a failure to create
         *	a new InputStream or Reader, or an illegal URL.
         */
        InputSource getExternalSubset(String name, String baseURI);
        //throws  SAXException, IOException;

        /**
         * Allows applications to map references to external entities into input
         * sources, or tell the parser it should use conventional URI resolution.
         * This method is only called for external entities which have been
         * properly declared.
         * This method provides more flexibility than the {@link EntityResolver}
         * interface, supporting implementations of more complex catalogue
         * schemes such as the one defined by the <a href=
        "http://www.oasis-open.org/committees/entity/spec-2001-08-06.html"
        >OASIS XML Catalogs</a> specification.</p>
         *
         * <p>Parsers configured to use this resolver method will call it
         * to determine the input source to use for any external entity
         * being included because of a reference in the XML text.
         * That excludes the document entity, and any external entity returned
         * by {@link #getExternalSubset getExternalSubset()}.
         * When a (non-validating) processor is configured not to include
         * a class of entities (parameter or general) through use of feature
         * flags, this method is not invoked for such entities.  </p>
         *
         * <p>Note that the entity naming scheme used here is the same one
         * used in the {@link LexicalHandler}, or in the {@link
        org.xml.sax.ContentHandler#skippedEntity
        ContentHandler.skippedEntity()}
         * method. </p>
         *
         * @param name Identifies the external entity being resolved.
         *	Either "[dtd]" for the external subset, or a name starting
         *	with "%" to indicate a parameter entity, or else the name of
         *	a general entity.  This is never null when invoked by a SAX2
         *	parser.
         * @param publicId The public identifier of the external entity being
         *	referenced (normalized as required by the XML specification), or
         *	null if none was supplied.
         * @param baseURI The URI with respect to which relative systemIDs
         *	are interpreted.  This is always an absolute URI, unless it is
         *	null (likely because the XMLReader was given an InputSource without
         *  one).  This URI is defined by the XML specification to be the one
         *	associated with the "&lt;" starting the relevant declaration.
         * @param systemId The system identifier of the external entity
         *	being referenced; either a relative or absolute URI.
         *  This is never null when invoked by a SAX2 parser; only declared
         *	entities, and any external subset, are resolved by such parsers.
         *
         * @return An InputSource object describing the new input source to
         *	be used by the parser.  Returning null directs the parser to
         *	resolve the system ID against the base URI and open a connection
         *	to resulting URI.
         *
         * @exception SAXException Any SAX exception, possibly wrapping
         *	another exception.
         * @exception IOException Probably indicating a failure to create
         *	a new InputStream or Reader, or an illegal URL.
         */
        InputSource resolveEntity(
            String name,
            String publicId,
            String baseURI,
            String systemId
        ); //throws  SAXException, IOException;
    }
}